Milling titanium: Balancing aggression with caution!

Titanium is intensely rewarding. It is resistant to oxidation and a long list of other chemicals. You can recycle it, and it is relatively light considering its strength, so you can see why Ti is a common thread among advanced industries like aerospace, automotive, medical and firearms. The payoff for mastering this material is undoubtedly big.

But there is a problem: The cost, length of the journey you must take to reach the promised land.

Titanium is extremely difficult to work. It seems like most CNC Machining accidents involve this incredibly difficult metal. The most experienced CNC professionals will apply extreme caution just to be sure they won’t break something.

How cautious?

Notice this footage is recorded at 12x speed!

And mistakes still happen no matter how much caution is applied!

Let’s face it. If we were burglars, titanium would be our Fort Knox. Everyone wants to break the last record surface speed, held unofficially by TITANS of CNC at 250 IPM. Their process is awesome to behold, but don’t try it at home!

In the next five minutes you’ll learn a bit more about what makes titanium and many of its alloys so difficult. You’ll see how to optimize your cuts, and above all, when to balance your aggression with caution.

Milling Titanium: Primary concerns are… everything

Titanium is used in a multitude of alloys, but the most common is Grade 5, just a hair’s breadth away from commercially pure titanium: 90% Ti and 6% Al and 4% V. Always be sure you understand what alloy you are using, as these vary considerably in their properties.

Titanium Milling Tactics

Ti makes amazing bloopers because it will crash your workholding attempts like an icepick through ice. That’s due to its flexibility. Instead of being cut it can bend, causing insane amounts of force on your workholding, as well as your cutting tool. Ti also tends to adhere, which ruins tools very quickly. These two characteristics lead to some cutting tactics that run 180 degrees counter to the norm.

  1. Always maintain uninterrupted contact between the tool and the block. Every entry point and exit carries the largest risks for failure, so you want to limit these as much as possible.
  2. Don’t attack the block head-on! Sliding the tool into cuts exposes much less of the tool surface to the block at any given time, which gives the tool less time to gain heat and more time to cool before the next rotation. Whenever possible, try to keep small arcs of the tool in active cutting.
  3. Climb-milling: Most metals require a thin-to-thick chip rate, meaning you start with a smaller chip rate and then increase after entry. But this strategy is absolutely wrong when applied to titanium. Instead, you want to start thick so that you break into the surface quickly, limiting the materials option for bending. On exit, you want to prevent adhesion with a thin chip.
  4. Another exit strategy is to mill a 45-degree chamfer at the end of the pass. This reduces the severity of the transition and avoids adhesion.
  5. Read Modern Machine Shop’s blog post on machining titanium for more great tips on how not to ruin your work or your tools while managing this upside-down metal. Read more. Read until your eyes bleed. It will take you more than five minutes, but the prep time will more than reward you come production.
  6. Find the right tool with more flutes. Titans of CNC used a 13-flute cutting tool because this keeps the chip rate low even with a fast surface speed. Generally you don’t want too many flutes, but if you can keep your radial depth low, then you can use more flutes.

Finding the right cutting tool for titanium can be like finding a needle in a haystack because you want as many flutes as possible, but how many depends on the project. Use MachiningCloud App to save you time selecting the right tool.

Good luck!

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